This invention relates to an apparatus and method for sealing the sidewise extending cover side flaps of a plurality of cartons which have been filled and which have had the cover closed and a front flap locked usually by means of a tongue, or spear, fitting in a slit in the front wall of the carton.
The following patents are believed to relate to the invention.
______________________________________ U.S. Pat. No. 2,974,460 Walther July 11, 1961 U.S. Pat. No. 2,991,610 Adacusky July 11, 1961 U.S. Pat. No. 3,267,637 Baker Aug. 23, 1966 U.S. Pat. No. 3,307,329 LeFief March 7, 1967 U.S. Pat. No. 3,523,398 Barnes Aug. 11, 1970 U.S. Pat. No. 3,740,919 Heisler June 26, 1973 U.S. Pat. No. 4,203,355 Meyers May 20, 1980 ______________________________________
Most of the prior art patents have attempted to solve the sealing of such flaps by advancing the filled, closed, cartons on timed, lower, registration chains having upstanding registration lugs which push the back of the carton and may damage the contents when the carton meets the resistance of fold bars, compression bars, or the like, during advance. Such push marks, or distortion of the carton is commercially unacceptable especially where the contents are food stuffs such as quick frozen fish.
Typical of the solutions of the above patents is that disclosed in Baker U.S. Pat. No. 3,267,637 wherein the cartons are advanced by registration lugs, front panel trailing while passing by adhesive application rolls, then under fold bars and then through compression rolls (Col. 4, lines 34-38).
In Barnes, U.S. Pat. No. 3,523,398, the end flaps of cartons are sealed by turning the carton through an angle of 90.degree., so that the cover flaps are on one side, whereupon the flaps are plowed open, adhesive applied, flaps closed and compression applied by plates. Barnes provides upper and lower untimed carrier belts but makes no provision for raising and lowering the height of the upper carriers, adhesive applicators and fold bars to accommodate cartons of various heights.
The prior art has not taught the use of untimed, upper and lower conveyor belts, resiliently yieldable compression rolls or an upper combined conveyor and hold down belt sub-frame structure which carries gently curved flap fold down bars, and is vertically movable relative to the lower conveyor belts.